The introductions of endoscopic surgical procedures and the newly developed, minimally invasive surgical procedures (those requiring very small incisions in the surgical patient) have brought great attention to the need for surgical instruments to facilitate the placement and securing of suture filaments within the surgical patient. The existing surgical graspers, holders, and passers have allowed surgeons to proceed with certain surgical procedures, even though the time to perform such procedures has been necessarily lengthened. This is due in part to the difficulty in securing the suture filaments. Many types of clips and fasteners have be en developed for securing sutures for maintaining the approximation of the tissue. Nevertheless, surgeons have shown a strong preference for using conventional surgical knots primarily because knots are reliable and do not require implanting foreign materials (other than the suture filament) into the surgical patient.
Certain surgical procedures require the placement of many knots in surgical sites within deep cavities or surgical apertures of the patient. On e such procedure, which is being performed by surgeons throughout the world, is the replacement of diseased and/or dysfunctional heart valves.
The particular valves most often requiring replacement, and for which successful surgical procedures have been developed, include the aortic valve located in the ascending aorta above the left ventricle, and the mitral valve located between the left atrium and the left ventricle of the heart. Healthy valves enable efficient cardiac function by providing unimpeded forward blood flow and preventing backflow into the originating chamber. These valves represent a very complex interplay between the valve leaflets, tendineae, muscles, and heart chamber walls. Unfortunately, the valves of the heart are susceptible to numerous, life-threatening diseases such as stenoses (a narrowing of the valve orifice) and regurgitation (or prolapse, when the valve leaflets do not coapt properly and thus are unable to prevent backflow.)
The trend for all surgical procedures, not only heart valve replacement, is to do the procedure less invasively and more quickly than before. The median sternotomy is still the most widely used means of access to the heart and greater vessels like the aorta. For a median sternotomy, a cut is made through the sternum of the surgical patient's chest, and a retractor is used to forcibly spread the left and right rib cages apart. The newer surgical procedures incorporate an intercostal (between the ribs) approach, also known as a thoracotomy, resulting in a much smaller wound and faster recovery time for the patient. The access, however, to the heart and greater vessels is more difficult with the thoracotomy, and use of the technique has necessitated the development of new surgical devices such as the present invention.
In an aortic valve replacement procedure, an incision is made into the ascending aorta to provide access to the valve. The leaflets of the valve are removed, leaving a thickened portion of the aortic wall known as the annulus. Next a mechanical or biological prosthesis is secured to the natural valve annulus using permanent sutures. Attachment of the prosthesis requires about 12 to 24 interrupted stitches. Each suture filament has a curved needle attached to each of the two free suture ends. A small pledget made from an implantable material is usually placed midway on the suture, and then one of the needles is passed through the valve annulus in a direction perpendicular to the plane of the annulus. The needle may be passed in the bottom-to-top direction so as to be able to view the needle tip piercing through the tissue. The needle may also be passed in the top-to-bottom direction. When both needles of a suture have been placed side-by-side into the annulus as described, the ends are drawn up out of the aorta so that the pledget rests against the tissue as reinforcement. A surgical clamp is normally locked onto the free ends of each pair of sutures and the clamp is then laid on the surgical drape covering the patient. The remaining sutures are likewise placed into the valve annulus, taking care to prevent the sutures from crossing over each other and becoming tangled. When all the sutures have been placed into the valve annulus of the aorta, the array of surgical clamps lying upon the patient serve to keep the sutures organized. Then one-by-one, each clamp is removed and each pair of needles on the respective suture is penetrated through the prosthetic valve. Next, the needles are trimmed off of the ends of the suture and the clamp is again locked onto the suture ends. Once all the sutures have been attached to the prosthesis, it is then "parachuted" into place inside the ascending aorta. Again one-by-one, the clamps are removed and the free ends of each suture pair is tied into a knot against the prosthesis which is at the bottom of the surgical aperture. To make one complete knot, the surgeon must tie one throw (alternating between a right and a left overhand slip knot) at a time, slide it down the suture and against the prosthesis using a fingertip or a knot-pushing device, then repeat the step five more times. The result of these steps is essentially three square knots tied in series. The excess suture is trimmed and the procedure is repeated for the remaining sutures. The time required to secure the sutures as described is a significant portion of the hours required to do the entire surgical procedure. A more detailed description of this surgical procedure may be found in Chapter 14 of Cardiac Surgery, Mosby's Perioperative Nursing Series, by Patricia C. Seifert, 1994.
In a busy operating room, there is an unfortunate opportunity for the surgeon to lose track of how many throws have been made when tying knots by hand, or whether the throws have been properly alternated between left and right which is necessary for an optimally secure knot. What is desired for this procedure and other surgical procedures requiring many knots to be placed in deep, surgical apertures, is a surgical device which can attach to two free ends of a suture filament already penetrated into tissue, and to place automatically all the alternating throws for each knot tightly and at the correct location on the surgical site. It is also desired to be able to use the surgical device to help manage the untied suture filaments.
Many devices for tying knots in suture filament within difficult-to-access surgical sites are described in the literature. None of the devices described are able to attach to two free ends of a suture filament already penetrated into tissue, the ends being attached to the device without tying a "pre-tied" knot into the filament, and to quickly and automatically place a secure knot at the surgical site. Several devices are described which have one end of the suture filament pre-tied and mounted on the distal end of the device, the other free end being attached to a needle. Examples are the following: U.S. Pat. No. 5,129,912 issued to Noda, et al on Jul. 14, 1992; U.S. Pat. No. 5,234,445 issued to Walker, et al on Aug. 10, 1993; U.S. Pat. No. 5,391,176 issued to de la Torre on Feb. 21, 1995; U.S. Pat. No. 5,454,820 issued to Kammerer, et al on Oct. 3, 1995; and U.S. Pat. No. 5,454,821 issued to Harm, et al on Oct. 3, 1995.
An instrument for tying and tightening ligature knots is described in a Russian Patent 2088162 to Bersenev, et al, and dated Aug. 27, 1997. This instrument has a coil spring with a single pre-tied loop stored in the hollow, distal end of a shaft. A hook on an end of the coil spring is attached to the suture filaments to be tied together. A pulling mechanism within the shaft is provided for unraveling the spring and transferring the single loop to the suture filaments. An apparent shortcoming of this instrument is the inability to deploy multiple loops into the suture filament in order to create a secure surgical knot similar to what surgeons are able to tie by conventional hand tying techniques. In addition, since the pre-tied loop is pulled through the stationary hollow, distal end of the shaft to transfer the knot to the suture, rather than the pre-tied knot being pushed off the distal end of the instrument, a portion of the tissue is drawn into the distal end of the instrument. This step appears to be traumatic to the tissue being sutured and could result in post-operative complications. What is needed is a way to transfer a pre-tied knot in a coil or equivalent element to the suture filament by pushing (rather than pulling) the pre-tied knot towards the tissue, so that tissue is not drawn into the distal end of the instrument.